The present invention relates generally to disk drive manufacturing methodology and more particularly to an improved method for manufacturing a disk drive wherein an integrated test system substantially reduces the labor involved in disk drive manufacturing and also substantially reduces the floor space required therefor. The improved method for manufacturing a disk drive also facilitates the application of statistical process control, so as to further enhance the efficiency of the manufacturing process.
Magnetic disk drives, such as those used for mass storage in personal computer systems, are well known. Referring to FIG. 14, a disk drive 162 comprises a head disk assembly (HDA)160 and a controller printed circuit board assembly (PCBA) 161. The HDA 160 comprises a cover 166, a base 167, one or more disks 165, a head stack assembly 163 for rotatably positioning a transducer 169 over a disk 165, and a spindle motor 164 for spinning the disks 165. The controller PCBA 161 comprises the electronic elements necessary to effect the writing of data upon the disks and the reading of data therefrom and for controlling the spindle motor 164 and the position of transducer 169 supported by head stack assembly 163.
The manufacturing of a disk drive comprises the separate fabrication and preliminary testing of the HDA 160 and the controller PCBA 161, which are subsequently mated and subjected to additional testing. This process is discussed in further detail below.
After HDA 160 has been fabricated, then servo writing is performed by securing HDA 160 to servowriter (not shown) in a well known process. During servo writing, servo information is written upon a surface of the disk 165. The servo information facilitates the precise positioning of transducer 169 over disk 165 during read and write processes.
After servo writing has been accomplished, HDA 160 is tested to preliminarily verify the validity of the servo information written upon disk 165. At this time an overlay is typically written to the disk to facilitate the later performance of an intelligent burn-in (IBI) test. A unique identification number is preferably also written to the disk at this time, so as to facilitate accurate tracking of the disk drive during the subsequent manufacturing processes. A bar code identification sticker may optionally be applied to HDA 160 as well.
Since the controller PCBA 161 has not yet been mated to the HDA 160, the above processes are performed utilizing non-deliverable electronics, i.e., electronics which are part of the test apparatus and which remain with the test apparatus. Servo writing and servo validity testing are performed within a clean room since the hard disk has not yet been environmentally sealed.
As mentioned above, the controller PCBA 161 is manufactured and tested separately from the HDA 160. Prior to leaving the clean room, the HDA 160 is environmentally sealed. Then typically outside the clean room, HDA 160 is mated to previously tested controller PCBA 161 so as to form a drive-under-test 162.
After leaving the clean room, a plurality, typically twenty-four, of such drives-under-test 162 are then loaded onto a tray. The tray provides for the mechanical attachment and the electrical connection of the drives-under-test 162 thereto, so as to facilitate simultaneous testing thereof. Thus, each individual drive-under-test 162 is electrically connected to the tray, then the tray is electrically connected to a test apparatus.
Once connected to the test apparatus, a power-on test is performed and then each drive-under-test 162 is checked to verify that it is ready for operation. Next, the basic operation of the drive-under-test 162 is checked. This includes testing each drive-under-test 162 for the proper performance of basic writing, reading, and seeking operations. The power-on test, drive ready test, and basic operational tests are referred to collectively herein as the initial drive test (IDT).
After successfully passing the IDT, each drive-under-test 162 is subjected to an intelligent burn-in (IBI). The IBI is preferably performed within an environmental chamber so as to facilitate testing at different temperatures, such as at ambient temperature and at 40-50xc2x0 C. The drive-under-test 162 test is conventionally performed by the drive as a stand-alone function, i.e. without connection to a host computer, because of its length and the relative scarcity of host connections available in prior art manufacturing installations. The IBI typically commences with a shortened version of the IDT, so as to verify basic functionality of the drive at both ambient and elevated temperatures. Next, a lengthy process comprising calibration of the drive and defect discovery and management is performed to set operating parameters and identify and map media defects which would affect the ability of the media to store information thereon reliably. Next, the drive-under-test 162 is formatted and the results of the IBI are stored thereon. Typically, 360 drives-under-test are subjected to the IBI simultaneously.
After successfully passing the IBI, each drive-under-test 162 is subjected to a final test. Final testing comprises connecting the drive-under-test 162 to a host computer, verifying operation of host commands, and analyzing the IBI test results and validating the same. Desired performance characteristics of the drive, such as head seek time, may be verified if desired. The IBI overlays are typically removed at this time, so as to prevent the drive from inadvertently being placed in the IBI mode by a customer. Any desired overlays, such as those required by a specific customer, for example, are written to the drive-under-test 162.
Various other tests may be performed on an individual drive-under-test 162 during a debug process when a fault is found during routine testing. Such debug tests are performed to isolate the fault, so as to facilitate the correction thereof. For example, a drive-under-test 162 may fail the disk write portion of the IDT and then have the problem isolated to a particular head assembly during the debug process.
Although the above-described manufacturing procedure has been found generally suitable for the production of reliable disk drives, it does possess inherent deficiencies which detract from the overall desirability thereof. For example, the IDT, the IBI, and the final test are each performed at separate stations. The use of such separate stations inherently requires substantial handling of the disk drives to move them from one test station to another. It also requires substantial floor space within the manufacturing facility to accommodate the necessary test equipment.
As those skilled in the art will appreciate, the handling of disk drives as they are transported between test stations is undesirable since it inherently lengthens the time required for the manufacturing process and also since costly manpower is required to facilitate such handling. This is of particular concern since disk drives are frequently manufactured overseas in areas where unemployment is very low and thus such workers may be difficult to find or retain during periods of expansion. Further, handling inherently increases the risk of damage to disk drives. For example, the drives may be subjected to shock or electrostatic discharge (ESD) damage, connectors may be misaligned, etc., during such handling. Such damage frequently necessitates costly re-work of the disk drive, further undesirably increasing the cost of manufacture thereof.
As those skilled in the art will further appreciate, it is desirable to minimize the amount of floor space required for any particular process within a manufacturing facility, so as to decrease the costs associated therewith. Such costs include the acquisition or lease cost of the space itself, as well as the cost of heating, cooling, cleaning, etc. associated with such space. Additionally, floor space is frequently the limiting factor affecting manufacturing capacity. Thus reducing the floor space required for a particular manufacturing process frequently results in increased manufacturing capacity.
The use of statistical process control to enhance the efficiency of various different manufacturing processes is also well known. Statistical process control facilitates the isolation of faulty manufacturing processes by statistically analyzing problems which are found in manufactured items. Such statistical analysis typically comprises the tabulation of specific problems and the comparison of the tabulation to pre-specified norms. When the actual incidence of a particular problem exceeds its expected norm, then steps are typically taken to correct the appropriate manufacturing process.
Further, when a plurality of substantially identical manufacturing processes are involved, then each manufacturing process may be compared to the others, rather than to pre-specified norms. For example, if a particular disk drive comprises six head assemblies, each associated with a particular disk surface, then the incidence of failure of a given head assembly may reasonably be expected to be approximately equal to that of the average of the remaining head assemblies. The observation of a higher than expected failure rate of a given head assembly, as thus compared to the average of the failure rates of the remaining head assemblies, indicates the need for corrective action.
As those skilled in the art will appreciate, the use of such statistical process control may potentially provide a substantial cost savings by substantially reducing the number of items which are manufactured improperly, thus requiring costly re-work.
As such, it is desirable to provide a method for manufacturing disk drives which substantially reduces the labor involved in the manufacturing process and which also substantially reduces the floor space required therefor. It is also desirable to isolate and correct faulty manufacturing processes as quickly as possible.
The present invention specifically addresses and alleviates the above-mentioned deficiencies associated with the prior art. More particularly, the present invention comprises a method for manufacturing a disk drive. The disk drive comprises a head assembly and a controller PCBA. The method comprises the steps of assembling a head disk assembly in a clean room, performing a head disk assembly test upon the head disk assembly in the clean room, connecting the head disk assembly to the controller printed circuit board assembly to form a drive-under-test, transporting the drive-under-test to an integrated test system and electrically connecting the drive-under-test to the integrated test system. Substantially all of the required manufacturing tests are performed upon the drive-under-test while the drive-under-test remains electrically connected to the integrated test system. These manufacturing tests comprise an initial drive test, an intelligent burn-in test, and a final test.
According to the preferred embodiment, the present invention further comprises the steps of monitoring the drive-under-test with a host computer while it is connected to the integrated test system and modifying an earlier performed manufacturing process when an indication is received by the host computer that the earlier performed manufacturing process is being performed improperly. This may be accomplished by analyzing statistical data resulting from the testing of many disk drives. An earlier performed manufacturing process may also be modified based upon the test results from a single drive, where those test results indicate the need for such modification.
Thus, statistical process control is utilized to provide an early indication that a particular manufacturing process is being performed improperly. The early detection and correction of such a faulty manufacturing process may potentially prevent the manufacture of a large number of faulty disk drives, particularly in high volume manufacturing facilities. As those skilled in the art will appreciate, the re-work of disk drives manufactured having an unacceptable defect due to a flawed manufacturing process can be extremely expensive.
Re-work of such improperly manufactured disk drives, if even possible, tends to be labor intensive, and therefore extremely costly. For example, if it is found that a number of drives have been manufactured with one defective head, then all of those drives must be disassembled, reassembled with a new head in place of the defective one, inspected, and retested.
A unique identification code is preferably written to the drive-under-test, preferably during head disk assembly testing. The identification code is used to determine which of a plurality of different manufacturing processes have been performed upon a particular drive-under-test, so as to facilitate modification of one of the manufacturing processes when an indication is received that one of the manufacturing processes is being performed improperly. Thus, the use of such a unique identification code facilitates easy identification of a particular manufacturing process, particularly when the plurality of such manufacturing processes are being performed simultaneously, i.e., in parallel with one another, i.e., simultaneously. Thus, the identification code facilitates the identification, for example, of the particular assembly line upon which the drive was fabricated.
The head disk assembly test preferably comprises verifying the validity of the servo writing process and writing intelligent burn-in overlays to the drive-under-test.
The initial drive test preferably comprises a power-on test, a check for drive ready, and a basic operational check of the writing, reading, and seeking processes.
The intelligent burn-in preferably comprises a check of the basic functionality of the drive-under-test, defect discovery and management, formatting of the drive-under-test, and writing of the burn-in test results onto the drive-under-test.
At least a portion of the intelligent burn-in is preferably performed with the drive-under-test at a temperature of between approximately 40xc2x0 C. at approximately 50xc2x0 C. Any of the tests performed while a drive-under-test is connected to the integrated test system may easily be performed under desired environmental conditions, e.g., at a desired temperature, since the integrated test system may easily be contained within an environmentally controlled facility and/or the integrated test system may optionally comprise an integrated environmental control system.
The final test preferably comprises analyzing and validating results of the intelligent burn-in, verifying performance characteristics of the drive-under-test 162, removing the intelligent burn-in overlays and writing any desired customer-specific overlays to the drive-under-test.
The step of electrically connecting the drive-under-test to the integrated test system comprises applying power to the drive-under-test, electrically setting jumpers upon the drive-under-test, and providing an electrical path for the communication of commands and data between the drive-under-test and the integrated test system. Alternatively, the jumper settings may be manually set prior to electrical connection of the drive-under-test 162 to the integrated test system. However, as those skilled in the art will appreciate, electrically setting jumpers upon the drive-under-test facilitates easy testing of the drive with different jumper settings, thereby enhancing the scope and effectiveness of such testing.
According to the preferred embodiment of the present invention, the step of connecting the head disk assembly to the controller printed circuit board assembly is performed outside of the clean room. Alternatively, the head disk assembly may be connected to the printed circuit board assembly inside the clean room.
The method for manufacturing a disk drive of the present invention thus substantially reduces the labor involved in disk drive manufacturing and also substantially reduces the floor space required therefor, as discussed in detail below. The present invention also facilitates the use of statistical process control, as also discussed in detail below.
These, as well as other advantages of the present invention will be more apparent from the following description and drawings. It is understood that changes in the specific structure shown and described may be made within the scope of the claims without departing from the spirit of the invention.